1. Field of the Invention
This invention relates to apparatus for controlling the operation of a combustion engine in response to an input command.
2. Description of the Prior Art
Automotive engineers have long recognized that a continuously variable transmission (CVT) can in theory be used to restrict a passenger car engine to a fixed operating schedule of throttle position versus crankshaft speed. The operating schedule has often been chosen to coincide with the line of minimum brake specific fuel consumption across the engine map of throttle position versus crankshaft speed.
Nevertheless, practical considerations have often received less emphasis. For instance, CVT's have yet to make a significant impact in passenger car use, not to mention large over-the-highway tractors. Moreover, a conventional transmission with a large number of closely-spaced gear ratios can have a more than offsetting advantage in ratio range in comparison to a CVT. More importantly, the prior art has failed to recognize the synergism between drive-by-wire control and the approximation of a CVT engine operating schedule using a discrete-ratio transmission. For example, in U.S. Pat. No. 4,353,272 Schneider et al disclose a drive-by-wire control system adaptable to both CV and discrete-ratio transmissions, but evidently without realizing that synergism exists only for the case of discrete-ratio transmissions. Equally important is the failure of the prior art to recognize that the same special engine calibration is optimum for both CVT and discrete-ratio transmissions.